1. Field of the Invention
The present invention relates to a toner recovery apparatus, a process cartridge, and an image forming apparatus, which are used for the formation of an electrophotographic image in an electrostatic copier, a laser printer, and the like.
2. Description of the Related Art
Recent demands for compact, high-speed, and low-cost electrostatic copiers and laser beam printers have prompted the development of compact, low-cost, and high-speed printers that are designed particularly for use in a small office or home office and for individual users.
Along with such a trend, full color laser printers that employ a tandem development system and an intermediate transfer method system are being predominated. Various makers have tried to downsize the integral process cartridge or the printer machine itself by devising the position or layout of the cartridge in the main body.
An example of a method for downsizing a process cartridge is to integrate all of the cartridge units including a toner hopper, a development unit, a cleaning unit, and a recovery unit for recovering a residual toner (hereinafter referred to as “waste toner”), and as one example of the configuration for downsizing the main body, various makers have marketed machines in which an intermediate transfer belt is placed horizontally and an integral process cartridge is disposed above the belt.
Particularly, in the case of such a main body configuration, since a transfer belt is disposed below a process cartridge, the physical relationship of units in the process cartridge will necessary be such that the developing and transferring unit is placed at the lowest part of the process cartridge and a toner hopper part (including a toner replenishing/stirring mechanism, and the like) and a waste toner recovery part are placed over the developing and transferring unit. If aiming at downsizing of a main body with such a configuration, the integral cartridge is designed so as to arrange the developing unit, hopper unit and waste toner recovery part in a vertical direction to minimize the area where the cartridge is disposed.
On the other hand, there have been conventionally proposed various means of transporting and collecting a waste toner removed in a cleaning part to a recovery unit, and a toner transfer method using a toner transporting belt has been proposed particularly as a waste toner recovery mechanism for a process cartridge with consideration of downsizing and cost reduction.
For example, Japanese Patent (JP-B) No. 3281595 describes a toner recovery apparatus as described below. That is, a process cartridge is provided with an endless groove in the side flame thereof, a side plate is fixed to the surface of the side frame formed with the groove in such a way that the groove is covered with this side plate, whereby a toner transporting duct is defined. This toner transporting duct is designed to have in the lower part thereof an inlet through which a waste toner enters from a cleaning unit, and this inlet is provided with a connection hole to communicate with the cleaning unit. Further, the toner transporting duct is designed to have in the upper part thereof an outlet provided with a connection hole to communicate with the toner recovery part. In addition, an endless toner transporting belt provided with a plurality of convex parts on the outer circumferential surface is housed so as to be rotatable along the groove. By rotating this toner transporting belt, a waste toner transported into the inlet from the cleaning unit is drawn up with the convex parts on the toner transporting belt, to transport in the outlet placed in apart above the inlet. The waste toner discharged by the toner transporting belt is collected in the toner recovery part by falling down into the toner recovery part from the outlet unit.
In Japanese Patent Application Laid-Open (JP-A) No. 08-15971, a toner transporting duct similar to the above described one is formed on a side surface of a process cartridge, which duct is defined by a waste toner transporting member and is gently inclined at an angle of about 30 degrees. This toner transporting duct is designed to have in the lower part thereof an inlet through which a waste toner enters from the cleaning unit, and this inlet is provided with a connection hole to communicate with the cleaning unit. Further, the toner transporting duct is designed to have in the upper part thereof an outlet provided with a connection hole to communicate with the toner recovery part. An endless waste toner transporting belt provided with a plurality of convex parts on the outer circumferential surface is provided in this toner transporting duct so as to freely rotate, and the waste toner transported into the inlet from the cleaning unit is transported toward the outlet while being scraped along with the bottom of the toner transporting duct by the convex parts on the toner transporting belt, and is collected in the toner recovery part.
However, the current situation is that the process cartridge with a vertical structure for achieving further reduced size in the above described related art still fails to realize sufficient performance as a waste toner recovery mechanism.
That is, in JP-B No. 3281595, although a waste toner is held against a toner transporting belt for transportation to the outlet, the toner transporting belt is oscillated by oscillation transmitted from a driving part, and the waste toner supported on the belt is spilled down from a gap between convex parts on the belt and the internal wall of the toner transporting duct by its own weight. The amount of the toner supported on the toner transporting belt therefore decreases on the way of toner transportation, whereby the toner transportation efficiency is lowered, and further, the toner particles spilled down still remains inside the transporting duct to cause clogging, thereby preventing rotation of the transporting belt. In JP-A No. 08-15971, the waste toner is transported in the outlet while being scraped along the bottom of the toner transporting duct by convex parts on the transporting belt. While such a transportation form is suitable for a horizontal process cartridge having a transporting duct with a comparatively gentle slope, however, in the case of necessarily taking a structure where the slope of the transporting duct has to be sharp, like a vertical process cartridge, the efficiency of transporting the waste toner disclosed in JP-A No. 08-15971 is insufficient, and in the same way as described in JP-B No. 3281595, there causes a problem where the waste toner on the way of transportation duct is spilled down from a gap between the bottom of the transporting duct and convex parts on the transporting belt.